"When your finger or hand touches a spot on the phone's lower left side - an easy thing, especially for lefties - the signal can significantly degrade enough to cause you to lose your connection altogether if you're in an area with a weak signal," said contributor Mike Gikas in a report on Consumer Reports' website.

Consumer Reports (www.consumerreports.org) publishes consumer guides based on its own personal findings on everything from technology products to motor vehicles. The organisation released a report stating that a problem does exist and also said that it has tested other smartphones - such as Apple's own iPhone 3GS and Palm's Pre - and found none of the signal-loss problems experienced with the iPhone 4.

Apple says it shifted 1.7 million iPhone 4s in the first three days since it was first introduced on the market.

Complaints about poor signal reception appeared almost immediately after the phone was picked-up by eager customers. The iPhone 4 uses a wraparound antenna and owners say that signal strength is affected heavily if the phone is touched in a certain way. Apple has since been sued by iPhone customers because of these problems.

Since the reception issues have come to light Apple has said that almost any cellphone will suffer a loss of signal if held in certain ways. The company later said it had discovered a software glitch that overstates signal strength, though it did not directly address concerns about the antenna with that admission.

Gikas suggested covering the gap in the wraparound antenna with duct tape or some other non-conductive material in an effort to avoid the reception problems.

Reception issues aside Consumer Reports said the iPhone 4 scored high in other test areas such as battery life, quality of display and the quality of its video/still image camera. However, Gikas said the signal problem was the reason the iPhone 4 would not be classified as a "recommended" device in its smartphone ratings.

"Apple needs to come out with a permanent - and free - fix to the antenna problem before we can recommend the iPhone4," said Gikas in his blog post on ConsumerReports.org.